The present invention relates to ignitors or detonators which are connected to a single two wire bus, in general and control systems which can individually communicate with or address individual ignitors over a two wire bus.
In many applications where a multiplicity of ignitors are used, it is desirable to be able to control the initiation and test of individual ignitors over a two wire bus. Using a bus architecture substantially reduces the total wiring required which typically reduces costs, and simplifies assembly of the ignitor arrangement. Such bus architectures addressing multiple ignitors can be used in a wide variety of applications ranging from a use in automobiles to initiate multiple safety systems in the event of a crash, to the use of various explosives in mining and geoseismology.
Recently, technology has been developed which employs microprocessors in combination with an ignitor which can be addressed over a data bus. These so-called smart ignitors allow information concerning the status of individual ignitors to be requested by a controller. The same controller can send an addressed signal to a particular ignitor causing it to begin internal testing, or to initiate an explosive or gas generating chemical charge.
The so-called smart ignitors bring new functionality and perhaps cost savings to many ignitor applications. However, such ignitors may not be desirable in all situations where it is desirable to be able to use a bus structure for communicating with multiple ignitors. In particular, a smart ignitor may require an integrated package between the ignitor and the microprocessor, which handles the protocols of bus architecture. In some applications it may be desirable to use different kinds of ignitors on the same bus. Or it may be desirable to use ignitors with relatively low volume production where integration of a microprocessor into the ignitor may not be cost-effective. In some applications repeaters may be necessary to assure that data signals can be transmitted over long bus wires.
What is needed is an ignitor system which can address multiple ignitors over a bus, to initiate the ignitors or to perform a functional test on the ignitors.
The ignitors and the ignitor control system of this invention employs individual ignitors which are connected to a bus through a unique bandpass filter. The ignitor control system generates a signal with a frequency corresponding to a bandpass filter associated with a particular ignitor. The signal either contains sufficient energy to initiate the ignitor or is set at a no-fire level, which can be used to detect the presence and integrity of a particular ignitor. Such a system requires no intelligence at the ignitor, the ignitor is a completely passive component until initiation, and the energy pulse can be tailored to the needs of a particular ignitor. Thus a pre-existing ignitor may be combined with a bandpass filter or a specially designed ignitor may incorporate a bandpass filter. A large number of individual ignitors may be placed on a single bus limited only by the frequency bandwidth of the bus, which is capable of transmitting the necessary power. For a twisted wire pair a reusable frequency range may extend between a few kHz and a few hundred kHz which might accommodate twenty or more unique frequencies which can be used to address 20 or more discrete initiators. A twisted wire pair might be usable at frequencies as high as 10 MHz.
The ignitor control system of the invention comprises two components: a controller for generating and receiving frequency pulses, and a voltage and current amplifier which provides the necessary voltage and current to test or initiate ignitors on the bus, and receives and conditions reflected signals received over the ignitor bus.
It is a feature of the present invention to provide an ignitor control system, which can function over long ignitor bus transmission lines.
It is another feature of the present invention to provide an ignitor control system, which can initiate and test with a multiplicity of ignitors connected in parallel to a bus.
It is a further feature of the present invention to provide an ignitor system which can uniquely communicate with ignitors on a bus where the individual ignitors are not required to have intelligence.
It is a still further feature of the present invention to provide an ignitor system which can function with ignitors that require different levels of energy, or combinations of current, voltage, and time to be initiated.
It is a yet further feature of the present invention to provide an ignitor system, which can perform passive tests on the individual ignitors, connected to a bus.
Further features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.